[CAUT] Restringing treble

[David Love]

My observation when a string breaks is that it tends to make the strings
on either side go sharp but progressively less as you move away from the
broken string.  That would seem to be consistent with some relaxing of
plate flex.  Cast iron is stiff but it does bend, as evidenced from the
plate flexing that is done to modify downbearing.  

David Love
davidlovepianos@comcast.net 

-----Original Message-----
From: caut-bounces@ptg.org [mailto:caut-bounces@ptg.org] On Behalf Of
A440A@aol.com
Sent: Friday, December 31, 2004 3:51 AM
To: caut@ptg.org
Subject: Re: [CAUT] Restringing treble

Greetings, 
  I wrote: 

I would think that it is the board rather than the plate.  When a string
breaks in the treble, the adjacent strings of that note seem to always
go sharp,  and when the string is replace, they come right back down.
Would 
one
string missing allow the plate to relax?, and if so, only on the
immediate
area?

David replies: 
<< I don't know.  One string breaking takes over 300 lbs off the plate
whereas it takes only a small percentage as a function of a change in
the deflection angle off the soundboard.  
David Love
   >>
And Ron writes: 
>>Would one string missing allow the soundboard to rise, and if so, only
in 
the immediate area? Got any idea how length change in a string affects 
pitch, and how much soundboard rise it takes at the existing bearing
angles 
to produce the length change necessary to affect the pitch difference 
observed?<<

What I wonder is why such a localized effect of losing a string?  Cast
iron 
is pretty stiff, and if losing a string allows the plate to relax,
wouldn't it 
affect more than just the two notes on either side?  I have measured 
soundboard drop under tension, and it isn't uncommon to see them drop
.050" when the 
piano is chipped to pitch.  Some more (such as the Chickerings with the
inner 
rim), some less (Steinways and Baldwins), but there is still a lot of
movement 
up and down. 
Regards, 


    




Ed Foote RPT 
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html
 
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